The answer about whether you can delete those folders depends on what's in them. If they only contain installers then Yes, if they have your LR catalog and photos or other files, then No.

The installer for LR on Windows is a little less than 1GB, and you have four or five folders, so that should be a little less than 4 or 5GB, but you say 6.8GB so maybe there are other things in those folders.